Lifespan: The Revolutionary Science of Why We Age—and Why We Don't Have To

by David A. Sinclair

We don’t count the age of a single yeast cell with birthday candles. They simply don’t last that long. Instead, aging in yeast is measured by the number of times a mother cell divides to produce daughter cells. In most cases, a yeast cell gets to about 25 divisions before it dies. That, however, makes obtaining old yeast cells an exceptionally challenging task. Because by the time an average yeast cell expires, it is surrounded by 225, or 33 million, of its descendants. It took a week of work, a lot of sleepless nights, and a whole lot of caffeinated beverages to collect enough regular old cells. The next day, when I developed the film to visualize the rDNA, what I saw astounded me.17 Just like the mutants, the normal old yeast cells were packed with ERCs. That was a “Eureka!” moment. Not proof—a good scientist never has proof of anything—but the first substantial confirmation of a theory, the foundation upon which I and others would build more discoveries in the years to come. The first testable prediction was if we put an ERC into very young yeast cells—and we devised a genetic trick to do that—the ERCs would multiply and distract the sirtuins, and the yeast cells would age prematurely, go sterile, and die young—and they did. We published that work in December 1997 in the scientific journal Cell, and the news broke around the world: “Scientists figured out a cause of aging.”

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